I am not Cathe( far from it actually!) But I would say not to worry about losing muscle. She is incorporating strength training into it with BootCamp, BodyMax, Step, Jump and Pump... If you want to increase your arms maybe incorporate an arm routine instead of where she has a 2nd workout. For instance instead of Low Max followed by Kickbox cardio. You do Low Max followed by an arm routine or something?? Just a thought. I am doing this rotation and loving it! Susan